IRF7946PbF

6

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Fig 14. Maximum Effective Transient Thermal Impedance, Junction-to-Case

Fig 15. Typical Avalanche Current vs.Pulsewidth

Fig 16. Maximum Avalanche Energy vs. Temperature

Notes on Repetitive Avalanche Curves , Figures 14, 15:

(For further info, see AN-1005 at www.irf.com)

1. Avalanche failures assumption:

Purely a thermal phenomenon and failure occurs at a temperature far in

3. Equation below based on circuit and waveforms shown in Figures 16a, 16b.

5. BV = Rated breakdown voltage (1.3 factor accounts for voltage increase

during avalanche).

7.

25°C in Figure 14, 15).

1E-006

1E-005

0.0001

0.001

0.01

0.1

t1 , Rectangular Pulse Duration (sec)

0.001

0.01

0.1

1

10

0.20

0.10

D = 0.50

0.02

0.01

0.05

SINGLE PULSE

( THERMAL RESPONSE )

Notes:

1. Duty Factor D = t1/t2

2. Peak Tj = P dm x Zthjc + Tc

1.0E-06

1.0E-05

1.0E-04

1.0E-03

1.0E-02

1.0E-01

tav (sec)

0.1

1

10

100

1000

Allowed avalanche Current vs avalanche

pulsewidth, tav, assuming

 j = 25°C and

Tstart = 125°C.

Allowed avalanche Current vs avalanche

pulsewidth, tav, assuming

Tj = 125°C and

Tstart =25°C (Single Pulse)

25

50

75

100

125

150

Starting TJ , Junction Temperature (°C)

0

10

20

30

40

50

60

70

80

90

TOP

Single Pulse

BOTTOM 1.0% Duty Cycle

ID = 90A